Diffuse leptomeningeal glioneuronal tumor mimicking chronic inflammatory and tuberculous meningitis.

Diffuse leptomeningeal glioneuronal tumors (DLGNT) are rare central nervous system neoplasms characterized by the absence of a primary brain or spinal cord tumor. Patients exhibit common radiological and histopathological features; however, the clinical progression varies. We present the case of a 4-year-old girl initially diagnosed with constipation and failure to thrive, who subsequently developed neurological signs during hospitalization. Subsequently, she was referred with suspected tuberculosis meningitis, despite negative cerebrospinal fluid (CSF) culture results, and the patient presumably started on anti-TB and methylprednisolone. Later, magnetic resonance imaging (MRI) demonstrated diffuse nodular meningeal enhancement, suggestive of infectious, autoimmune, or neoplastic etiologies. Further histopathological examination confirmed DLGNT by identifying atypical glial cells, lymphohistiocytic infiltrate, fibrosis, and the presence of the BRAF V600E mutation. Given the rarity of the condition and its recent recognition in the World Health Organization (WHO) classification, many clinicians may be unfamiliar with DLGNT. Consequently, molecular diagnosis is essential, as exemplified in this case.